Earthquakes
Chapter 9
Forces Inside Earth
Section 9.1
Causes of Earthquakes
What causes an earthquake?
Forces Inside Earth
Earthquakes are caused by the sudden release of stress built up in rocks inside earth.
Forces Inside Earth
What is a fault?
Forces Inside Earth
Fault surface along which rocks break inside earth
Types of Faults
List the types of faults.
Types of Faults
Three types of Faults:
Normal
Reverse
Strike-Slip
Types of Faults
What are the types of forces causing earthquakes?
Types of Faults
Three types of forces:
Tension
Compression
Shear
Types of Faults
Describe each type of force.
Types of Faults
Three types of forces:
Tension pull apart
Compression push together
Shear side-by-side (parallel but not inline)
Types of Faults
Describe the difference in a foot wall and a hanging wall along a fault.
Types of Faults
Foot wall rock below the fault
Hanging wall rock above the fault
Types of Faults
Describe a Normal fault.
Types of Faults
Normal Fault
Tension forces
Rocks pull apart
Hanging wall slides down foot wall
Types of Faults
Reverse Fault
Compression forces
Rocks push together
Hanging wall slides up the foot wall
Types of Faults
Strike-Slip (Transverse) Fault
Sheer forces
Rocks move parallel to each other
Hanging wall and foot wall move horizontal (neither up nor down)
Earthquake Information
Section 9.2
Types of Seismic Waves
What are Seismic Waves?
Types of Seismic Waves
Seismic Waves Earthquake waves
Types of Seismic Waves
Give the types of Seismic Waves.
Types of Seismic Waves
Classification of Seismic Waves
Body waves
P-Waves(Primary waves)
S-Waves(Secondary waves)
Surface waves
Types of Seismic Waves
Describe each type of Seismic Waves.
Types of Seismic Waves
Classification of Seismic Waves
Body waves - waves inside the earth
P-Waves(Primary waves)
Compressional waves rocks vibrate in the same direction as the wave travels
Fastest wave
First to arrive
Weakest wave
Types of Seismic Waves
Classification of Seismic Waves(Cont.)
Body waves - waves inside the earth
S-Waves(Secondary waves)
Transverse waves rocks vibrate at a right angle to the direction the wave travels
Slowest body wave
Second to arrive
Strongest body wave
Types of Seismic Waves
Classification of Seismic Waves(Cont.)
Surface waves waves on the surface of earth
Elliptical and back and forth motion
Slowest
Last wave to arrive
Causes most damage
Types of Seismic Waves
What is the difference in the epicenter and the focus?
Types of Seismic Waves
Focus
Inside earth
Where rocks slip
Location of earthquake
Epicenter
On surface of earth
Above the focus
Where earthquake is first felt on earth
Locating an Epicenter
What is a Seismograph?
Locating an Epicenter
Seismograph device used to measure the strength and time of arrival of a seismic wave.
Locating an Epicenter
How can the Epicenter of an earthquake be located?
Locating an Epicenter
Triangulation is used to find the location of an earthquake.
Need to know the distance the earthquake is from three location.
Draw a circle around each location with radius of the distance.
The epicenter is where the circles intersect
Using Seismic Waves to Map Earths Interior
How are seismic waves used to "see" inside the earth?
Using Seismic Waves to Map Earths Interior
Primary and secondary waves
slow down when they hit plastic(soft) material
Speed up at solid(hard) material
Secondary waves
Will not travel through liquid
Primary waves
Slowed and refracted(change direction) by liquid
Speed up in solid(hard) material
Using Seismic Waves to Map Earths Interior
What is the result of differences in waves?
Using Seismic Waves to Map Earths Interior
Layers of the Earths interior:
Crust - solid
Mantle silicon, oxygen, magnesium, iron
Outer core liquid(iron, nickel)
Inner core solid (iron, nickel)
Using Seismic Waves to Map Earths Interior
What is the Moho Discontinuity?
Using Seismic Waves to Map Earths Interior
Moho discontinuity dense layer between the crust and the mantle.
Using Seismic Waves to Map Earths Interior
Other layers of the Earth
Lithosphere crust and upper mantle
Asthenosphere plastic lower mantle
Core
Destruction by Earthquakes
Section 9.3
Measuring Earthquakes
What is Seismology?
Measuring Earthquakes
Seismology Study of earthquake waves
Seismograph instrument used to record primary, secondary, and surface waves
Seismologists Scientist who study earthquakes and seismic waves
Measuring Earthquakes
What is the Richter scale and how does it work?
Measuring Earthquakes
Richter scale describes how much energy is released by the earthquake
Measuring Earthquakes
An increase of 1 on the Richter scale is 32 times more energy.
8.5 earthquake is 32 time stronger than a 7.5 earthquake.
32N = increase in strength
Where N = number of magnitudes
Tsunamis
What is a Tsunamis?
Tsunamis
Tsunamis seismic sea wave caused by earthquakes
Earthquake Safety
How can your home be made more Earthquake proof?
Earthquake Safety
Quake-Proofing Your Home
Take heavy objects down from high shelves
See that hot-water heaters and gas appliances are held securely in place
Keep away from windows and avoid anything that could fall on you during an earthquake
Watch for fallen power lines and possible fire hazards.
Stay clear of rubble that could contain sharp edges.
